let's go to cnn pentagon correspondent barbara starr in washington. barbara? >> the big concern here in washington is a ground war in gaza. there is growing concern that israeli troops and tank forces might cross the border and move into gaza. that is the major escalation that the u.s. does not want to see. so, the calculation now is, what does it take to make hamas stop its rocket attacks into israel and israel feel comfortable enough with that to pull back on the air strikes and pull back on any ground forces that it is assembling near the gaza border. there has been a lot of diplomacy going on. defense secretary leon panetta traveling in asia, calling the israeli defense minister barack. secretary of state hillary clinton firing up the diplomatic phone lines calling israel, turkey and jordan. randi? >> barbara starr in washington, thank you. as you can see, cnn has every angle covered on this story. >>> much more ahead this hour. here's a look at what we have coming up. >>> on the brink of war. as fighting escalates between israel and hamas, experts say the